Vehicle body structure

ABSTRACT

In a vehicle body structure, a frontal crash performance is improved by establishing a transmission path of a frontal crash load by a floor frame ( 28 ) without increasing the weight of the vehicle body, manufacturing cost or the number of welding spots. The floor frame ( 28 ) is attached to a lower surface of a floor panel ( 12 ), and extends from a rear end of a front side frame ( 20 ) from a longitudinally intermediate part of the floor panel. A rear part of the floor panel is formed with a side bead ( 34 ) extending in a fore and aft direction in alignment with the floor frame. The rear end of the floor frame is connected to the front end of the side bead via a slope section ( 32 ) of the floor panel, and the rear end of the side bead is connected to a middle cross member ( 18 ) extending laterally along the rear edge of the floor panel.

TECHNICAL FIELD

The present invention relates to a vehicle body structure, and inparticular to a vehicle body floor structure.

BACKGROUND OF THE INVENTION

In the field of vehicle body structure, it is known to connect a rearend of each front side frame to front ends of a front inside sill and acenter frame via an outrigger or the like (See JP 2009-18725A, forinstance), and to use a floor frame extending in the fore and aftdirection between each front inside sill and a center frame (floortunnel frame) and having a front end connected to the rear end of afront side frame and a rear end connected to a middle cross memberlocated under the rear seat (See JP 2009-6902A and JP 2009-6903A, forinstance).

The floor frames allow the frontal crash load applied to the front sideframes to be transmitted to the rear part of the vehicle body via thefloor frames in addition to the front inside sills and center frame. Bythus increasing the possible paths of the frontal crash load, thetransmission of the frontal crash load to the rear part of the vehiclebody is performed in a highly efficient manner, and this improves thecrash performance of the vehicle body. Furthermore, by welding the floorframes to the floor panel, the stiffness of the floor panel isincreased, and this contributes to the NV (noise and vibration)performance of the vehicle body.

However, according to the prior proposal, as the floor frames extendover the entire fore and aft extent of the floor panel, the weight ofthe vehicle body may undesirably increase. Furthermore, the increasednumber of welding spots increases the manufacturing cost and reduces themanufacturing efficiency.

Also, in an automotive floor structure, it has been proposed to stampform dimples defined by a three-dimensionally curved surface in thefloor panel with the aim of increasing the stiffness of the floor paneland improving the NV performance of the vehicle body. See (See JP2004-237871A, for instance).

However, the dimples prevent the floor panel to provide a flat floorsurface. In particular, if the dimples extend over large areas anddefine gradual curves, the carpet placed on the floor surface followsthe contour of the dimpled floor surface, and this impairs the comfortof the vehicle occupant. If the floor surface includes slanted areas,the vehicle occupant may be unable to stand of the floor in a stablemanner. If the vehicle occupant moves about on the floor, his or herfoot may stumble upon floor irregularities, and may experience somediscomfort.

Conventionally, such problems were overcome by placing a thick under padtypically made of thick urethane mat or a stiff board under the carpet.But this requires an additional component, and impairs the productionefficiency, manufacturing cost and resources saving efforts.

BRIEF SUMMARY OF THE INVENTION

In view of such problems of the prior art, a primary object of thepresent invention is to provide a vehicle body structure incorporatedwith a floor frame which is effective in transmitting a frontal crashload to a rear part of the vehicle body without excessively increasingthe weight of the vehicle body.

A second object of the present invention is to provide a vehicle bodystructure incorporated with a floor frame which is effective intransmitting a frontal crash load to a rear part of the vehicle bodywithout excessively increasing the manufacturing cost or impairing themanufacturing efficiency.

A third object of the present invention is to provide a vehicle bodystructure which provides a flat carpeted floor surface while increasingthe stiffness of the floor panel without increasing the weight of thevehicle body.

According to the present invention, such objects can be accomplished byproviding a vehicle body structure, comprising: a pair of front sideframes each extending in a fore and aft direction; a floor panel havinga front end connected to rear ends of the front side frames andextending rearward from the front end thereof in a substantiallyhorizontal direction; a first middle cross member extending laterally ina rear end of the floor panel; a pair of floor frames attached to alower surface of the floor panel, and each provided with a front endconnected to a rear end of the corresponding front side frame and a rearend reaching at least to an intermediate part of the floor panel in thefore and aft direction; and a pair of side beads each having a front endconnected to a rear end of the corresponding floor frame and extendingrearward therefrom in the fore and aft direction to the first middlecross member.

Each floor frame and corresponding side bead formed in the floor paneljointly establish a transmission path of a frontal crash load thatreaches the first middle cross member. The side bead allows thenecessary fore and aft length of the floor frame to be reduced, and thisin turn reduces the weight of the vehicle body and reduces the number ofwelding spots.

According to a preferred embodiment of the present invention, a rearpart of the floor panel is formed with a foot rest recess recessed froma remaining part of the floor panel, a front end of the foot rest recessincluding a slope section inclining upward toward a front part of thefloor panel, and wherein the side bead extends across the foot restrecess in the fore and aft direction, and has a front end connected to arear end of the corresponding floor frame at the slope section in linearalignment with each other.

The foot rest recess increases the leg room of the vehicle occupantseated in the rear seat. As the rear end of the floor frame abuts theslope section of the floor panel 12, the slope section increases themechanical strength of the front part of the side bead. As the floorframe is connected linearly to the side bead at the slope section, thetransmission of the frontal crash load from the floor frame to the sidebead can be effected in an efficient manner. Preferably, the rear end ofthe floor frame is overlaid on an outer periphery of the front end ofthe corresponding side bead by a certain longitudinal length.

Thereby, the floor frame and side bead can be connected to each otherwith a high mechanical strength, and this allows the frontal crash loadfrom the floor frame to be transmitted to the side bead in an efficientmanner. The vehicle body structure of the present invention preferablyfurther comprises a second middle cross member extending laterallyimmediately in front of the slope section.

The second middle cross member increases the mechanical strength of theslope section, and this enhances the favorable transmission of thefrontal crash load from the floor frame to the side bead via the slopesection.

According to a preferred embodiment of the present invention, each sidebead is formed as a groove having an open end facing upward, and a wireharness is received in the groove defined by the side bead.

Thereby, the side bead can be conveniently utilized as a conduit forreceiving the wire harness inside the passenger compartment. Also, byfilling the groove defined by the side bead with the wire harness, thecarpet placed on the floor surface is enabled to provide a flat floorsurface.

According to a certain aspect of the present invention, the vehicle bodystructure may further comprise a pair of side sills extending in thefore and aft direction along either side edge of the floor panel; acenter frame extending in the fore and aft direction along alongitudinal center line of the floor panel; and a pair of connectingmembers each having a front end connected to a rear end of thecorresponding front side frame and a pair of bifurcated rear endsconnected to a front end of the corresponding side sill and a front endof the corresponding center frame, respectively; wherein a crotchportion of each connecting member is connected to a front end of thefloor frame, and each front side frame and the corresponding floor frameare connected in mutual alignment in the fore and aft direction in planview via the corresponding connecting member.

Thereby, the frontal crash load applied to each front side frame istransmitted in the fore and aft direction not only by the path definedby the floor frame and side bead of the floor panel, but also by the twoother paths defined by the side sill and center frame, respectively.This reduces the requirement of the floor frame and side bead towithstand the frontal crash load, and enables a compact and light weightdesign of the floor frame. In this case, the floor panel may be providedwith a center tunnel section bulging upward and extending in the foreand aft direction in a laterally central position of the floor panel,while the center frames extend along either side end of the centertunnel section.

According to another aspect of the present invention, a part of thefloor panel adjoining the center tunnel section includes a slopingsection inclining upward toward the center tunnel section and ahorizontal terraced section connected to an inboard side of the slopingsection, and an outboard side of each center frame comprises a flangeoverlaid and welded to the terraced section.

As the sloping section is defined by folding lines of the floor panel,the presence of the sloping section increases the stiffness of theadjoining region so that the stiffness of the center frame can beeffectively increased.

According to yet another aspect of the present invention, the floorpanel includes a downward bulge having a bottom surface recessed from ageneral surface of the floor panel, and at least one bead projectingupward from a bottom wall of the downward bulge and having a top surfacesubstantially at a same elevation as the general surface.

The downward bulge increases the stiffness of the floor panel. As thebead formed within the downward bulge prevents the sagging or droppingof the carpet into the downward bulge, the need for an additionalcomponent such as an under pad for preventing the sagging of the carpetcan be eliminated. Furthermore, the bead formed within the downwardbulge further increases the stiffness of the floor panel.

If the side bead extends in the fore and aft direction laterallyadjacent to the downward bulge, the required stiffness of the floorpanel can be achieved without unduly increasing the size of the downwardbulge.

Thus, according to the present invention, owing to the cooperationbetween each floor frame and the corresponding side bead formed in thefloor panel, a transmission path of the frontal crash load can beestablished between the front side frame and first middle cross member.The presence of the side bead allows the length of the floor frame to bereduced, and this allows a corresponding reduction in the vehicle weightand the number of welding spots. Therefore, a high crash performance canbe achieved with a minimum cost and without impairing manufacturingefficiency.

Also, by providing a downward bulge and a bead projecting upward fromthe bottom wall of the downward bulge, the stiffness of the floor panelcan be increased without impairing the flatness of the floor surfacewhen the floor panel is covered by a carpet. This is accomplishedwithout adding any extra component and without impairing productionefficiency, manufacturing cost and resources saving efforts.

BRIEF DESCRIPTION OF THE DRAWINGS

Now the present invention is described in the following with referenceto the appended drawings, in which:

FIG. 1 is a fragmentary bottom view of the floor section of a vehiclebody structure embodying the present invention;

FIG. 2 is a fragmentary plan view of the floor section shown in FIG. 1;

FIG. 3 is a fragmentary sectional side view of the floor section shownin FIG. 1;

FIG. 4 is an enlarged fragmentary sectional side view taken along lineIV-IV of FIG. 1;

FIG. 5 a fragmentary cross sectional view taken along line V-V of FIG.1; and

FIG. 6 is a fragmentary perspective rear view of a rear seat mounted onthe rear floor section shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 6, a vehicle body embodying the presentinvention is essentially formed by stamp forming steel sheet and weldingthe stamp formed steel sheet components to each other. As this vehiclebody structure is in most part symmetric about a central longitudinalline, the following discussion may refer only to one side of the vehiclebody structure where appropriate to avoid redundancy of the description.

A front part of the vehicle body includes dashboard panel 10 separatingan engine room from a passenger compartment, and a lower end of thedashboard panel 10 is connected to a front end of a horizontallyextending floor panel 12 that generally defines the floor of thepassenger compartment.

Each side edge of the floor panel 12 is connected to a side sill 14defining a rectangular closed cross section and extending in the foreand aft direction. The cross section of the side sill 14 is somewhatvertically elongated, and the side edge of the floor panel 12 is weldedto a lower end of an inboard side wall of the side will 14. The rear endof each side sill 14 is connected to the front end of a side sillextension 16 also having a rectangular closed cross section.

The rear edge of the floor panel 12 is connected to a first middle crossmember 18 having a rectangular closed cross section and extendingbetween the right and left side sill extensions 16. The first middlecross member 18 is also connected to a front edge of a trunk floor panel(which extends horizontally but somewhat higher than the floor panel 12)not shown in the drawings, and defines a kick-up portion between the twofloor panels.

From each side end part of the dashboard panel 10 extends a front sideframe 20 in the forward direction or to the side of the engine room. Thefront side frame 20 also has a rectangular closed cross section and hasa rear end connected to a corresponding connecting member 22.

The connecting member 22 is provided with a rectangular closed crosssection and attached to the front side of the dashboard panel 10 at thefront end part thereof as best illustrated in FIG. 3. The connectingmember 22 is bifurcated toward the rear part thereof into an outriggersection 22B extending from a connecting section 22A obliquely in theoutboard direction and connected to the front end of the correspondingside sill 14 and a center frame extension section 22C extendingobliquely from the connecting section 22A in the inboard direction andconnected to the front end of a center frame 24 (which will be describedhereinafter).

The floor panel 12 is provided with a center tunnel section 26 in alaterally middle part thereof so as to bulge upward and extend in thefore and aft direction, and the rear end of the floor panel 12 isconnected to the first middle cross member 18. The center tunnel section26 may be formed welding a sheet metal component to the floor panel 12as is the case with the illustrated embodiment, but may also be formedas a part of the floor panel 12 when stamp forming the floor panel 12.Each center frame 24 is provided with a channel cross section, and isattached to the bottom surface of the floor panel 12 adjacent to thecorresponding side of the center tunnel section 26 so as to jointlydefine a rectangular closed cross section. The rear end of the centerframe 24 is connected to the first middle cross member 18.

As best illustrated in FIG. 1, a floor frame 28 extends in the fore andaft direction laterally intermediate between each side sill 14 and thecorresponding center frame 24, and is attached to the bottom surface ofthe floor panel 12 so as to jointly define a rectangular closed crosssection. The front end of the floor frame 28 is connected to a crotchpart 22D between the outrigger section 22B and center frame extensionsection 22C. Thereby, each floor frame 28 extends in alignment with thecorresponding front side frame 20 in the fore and aft direction via thecorresponding connecting member 22.

A rear half part of the floor panel 12 is formed with a pair of footrest recesses 30 on either side of the center tunnel section 26 where avehicle occupant in the rear seat usually places his or her feet. Eachfoot rest recess 30 is recessed downward with respect to a main surface11 (see FIG. 5) of the floor panel 12, and extends in the fore and aftdirection from an intermediate point of the floor panel 12 to the rearend of the floor panel 12. In other words, a bottom surface (generalsurface) 12A of each foot recess 30 is slightly lower than the mainsurface 11 of the floor panel 12. It should be noted that the footrecesses 30 are optional, and not essential for the present invention orthe general surface 12A may be on the same plane as the main surface 11if desired.

The front end of each foot rest recess 30 is connected to the remainingpart of the floor panel 12 via an upward slope section 32. The rear endof each floor frame 28 abuts the upward slope section 32 from the bottomsurface thereof as will be described hereinafter.

A channel having an open upper end or a side bead 34 is formed in thefloor panel 12 so as to extend across each foot rest recess 30 in alaterally middle part thereof in the fore and aft direction. The sidebead 34 protrudes downward from the floor panel 12, and aligns with thefloor frame 28 in the fore and aft direction as seen in plan view.

The front end of each side bead 34 is connected to the correspondingfloor frame 28 at the slope section 32 of the floor panel 12. The rearend of the side bead 34 is connected or welded to the front wall of thefirst middle cross member 18.

Each floor frame 28 is provided with a channel cross section slightlylarger than the channel cross section of the side bead 34 so that therear end of the floor frame 28 overlaps with the front end of the sidebead 34 over a certain length L (see FIG. 4) extending at least partly(or mostly) over the slope section 32 of the floor panel 12 in the foreand aft direction. The rear end of the floor frame 28 abuts the front orlower surface of the slope section 32, and may be welded thereto.

The part of the bottom wall of each foot rest recess 30 located betweenthe corresponding side bead 34 and center frame 24 is formed with adimple 50 or an elliptic recess or bulge protruding downward from thefloor panel 12. The dimple 50 may be defined by an ellipsoid ofrevolution or other smooth depression, typically elongated in the foreand aft direction, and is defined by a corresponding three-dimensionallycurved surface. The provision of the dimples 50 increases the stiffnessof the floor panel 12, and improves the NV performance thereof. However,the shape of the dimples in the illustrated embodiment is purelyexemplary, and can be selected as long as it increases the stiffness ofthe floor panel 12.

A pair of beads 52 each elongated in the fore and aft direction areformed laterally centrally in the bottom wall of each dimple 50 onebehind the other. Each bead 52 is provided with a relatively flat topsurface 52A at a same elevation as the general surface 12A.

A carpet 42 is laid over the general surface 12A of the floor panel 12.Owing to the presence of the beads 52 in each dimple 50, the carpet 42is prevented from dropping or sagging into the dimple 52. The beads 52may act as stepping stones in each dimple 50. It were not for the beads52, the carpet 42 would follow the contour of the curved inner surface50A of the dimple 50, and the flatness of the floor surface may beimpaired. Therefore, even when the carpet 42 is not provided with undulyhigh thickness or stiffness, a flat floor surface may be achievedwithout adding any stiff floor board or carpet liner.

Furthermore, the beads 52 enhance the performance of the dimples 50 inimproving the NV performance of the floor panel 12.

As best shown in the cross sectional view of FIG. 5, the part of thefloor panel 12 intermediate between the foot rest recess 30 and thecenter frame 24 includes a sloping section 12B inclined upward in theinboard direction. A horizontally extending terraced section 12C isconnected to the inboard side of the sloping section 12B. The terracedsection 12C may have a same elevation as the general surface 12A of thefloor panel 12. An outboard flange of the center frame 24 is overlaidwith the lateral edge of the center tunnel section 26 and the floorpanel 12, and are welded to each other.

The sloping section 12B which consists of a bent section of the floorpanel 12 contributes to the improvement in the stiffness of the floorpanel 12. This allows the necessary lateral width of the dimple 50 to beminimized so that the carpet 42 is made less prone to dropping into thedimple 50.

In the illustrated embodiment, the beads 52 are located well inside eachdimple 50, and not adjacent to the periphery thereof so that a stressconcentration in the peripheral part of the dimple 50 can be avoidedwhen stamp forming the floor panel 12 including the dimples 50.

Each side bead 34 is located adjacent to the outboard side of thecorresponding dimple 50. As the side bead 34 is formed by bulging thefloor panel 12 in downward direction, a space defined by the side bead34 and carpet 42 can be conveniently used for receiving a wire harness40 therein. The presence of the wire harness 40 in each side bead alsocontributes to defining a flat floor surface by filling the groovedefined by the side bead 34. The presence of the side bead 34 increasesthe stiffness of the floor panel 12, and this also allows the necessarylateral width of the dimple 50 to be minimized so that the carpet 42 ismade less prone to dropping into the dimple 50.

Thus, a relatively flat floor surface can be achieved in spite of thepresence of the dimples 50 and side beads 34. If desired, a melt sheet44 may be attached to the upper surface of a selected area of the floorpanel 12 to further enhance the NV performance of the floor panel 12.

As best illustrated in FIG. 2, a second middle cross member 36 extendslaterally from an intermediate part of the center tunnel section 26 toeach side sill 14. The second middle cross member 36 is provided with achannel cross section having an open end facing downward, and is weldedto the upper surface of the floor panel 12 along side flanges of thesecond middle cross member 36 so as to jointly define a closed crosssection. The second middle cross member 36 is located immediately aheadof the slope section 32.

In this vehicle body structure, the frontal crash load applied to thefront side frames 20 is transmitted to the rear part of vehicle via aplurality of paths:

-   (1) front side frame 20→outrigger section 22B→side sill 14→side sill    extension member 16→first middle cross member 18;-   (2) front side frame 20→center frame extension section 22C→center    frame 24→first middle cross member 18; and

(3) front side frame 20→crotch part 22D of the connecting member22→floor frame 28→side bead 34→first middle cross member 18.

In particular, as best illustrated in FIG. 1, each floor frame 28 alignswith the corresponding front side frame 20 in plan view so that thetransmission of the frontal crash load along path (3) can be effected ina favorable and efficient manner without causing any undue bendingmoment.

The side bead 34 serves as a rear extension of the floor frame 28, andprovides a similar effect as rearwardly extending the floor frame 28 inachieving a required crash performance Therefore, the weight of thevehicle body can be reduced owing to the elimination of the need for anextension of the floor frame 28, and the efficiency of the assembly workcan be improved owing to the reduction in the number of welding spots.

The frontal crash load applied to each front side frame 20 istransmitted to the rear part of the vehicle body not only via the pathdefined by the floor frame 28 and side bead 34 but also via the twoadditional paths defined by the side sill 14 and center frame 24.Therefore, the crash load is distributed between the three transmissionpaths so that the floor frame 28 can be made more compact and light inweight.

The second middle cross member 36 allows the frontal crash load appliedto the floor frame 28 to be distributed between the side sill 14 andcenter frame 24, and this allows the floor frame 28 to be made morecompact and light in weight owing to the reduced strength/stiffnessrequirements.

In this vehicle body structure, because the rear end of the floor frame28 abuts and welded to the slope section 32 of the floor panel 12, andis linearly connected to the side bead 34 at the slope section 32, thefrontal crash load applied to the floor frame 28 can be efficientlytransmitted to the rear part of the vehicle body via the side bead 34.

The second middle cross member 36 provided adjacent to the slope section32 reinforces the slope section 32 so that the transmission of thefrontal crash load from the floor frame 28 to the side bead 34 can beeffected in a favorable manner. Furthermore, as the rear end of thefloor frame 28 complementarily overlaps with the outer periphery of thefront end of the side bead 34, an adequate mechanical strength isensured to the junction between the two parts, and this also contributesto the favorable transmission of the frontal crash load.

As the side bead 34 defines a groove facing or opening out to thepassenger compartment, it can be conveniently used for receiving wireharnesses 40 which may include power lines and signals lines as shown inFIGS. 2 and 5. By suitably selecting the dimensions of the side bead 34and wire harnesses, a flat floor surface may be created with the aid ofthe carpet 44 as shown in FIG. 5.

The floor frame 28 was connected to the front side frame 20 via theconnecting member 22 in the illustrated embodiment, but the presentinvention is not limited by this embodiment. For instance, the floorframe 28 may be directly connected to the front side frame 20, or theconnecting member 22 may consist of an integral extension of the floorframe 28 without departing from the spirit of the present invention.

Although the present invention has been described in terms of apreferred embodiment thereof, it is obvious to a person skilled in theart that various alterations and modifications are possible withoutdeparting from the scope of the present invention which is set forth inthe appended claims.

The contents of the original Japanese patent applications on which theParis Convention priority claim is made for the present application aswell as any prior art references or copending applications mentioned inthis application are incorporated in this application by reference.

The invention claimed is:
 1. A vehicle body structure, comprising: apair of front side frames each extending in a fore and aft direction; afloor panel having a front end connected to rear ends of the front sideframes and extending rearward from the front end thereof in asubstantially horizontal direction; a first middle cross memberextending laterally in a rear end of the floor panel; a pair of floorframes attached to a lower surface of the floor panel, and each providedwith a front end connected to a rear end of the corresponding front sideframe and a rear end reaching at least to an intermediate part of thefloor panel in the fore and aft direction; a pair of side beads eachhaving a front end connected to a rear end of the corresponding floorframe and extending rearward therefrom in the fore and aft direction tothe first middle cross member; a pair of side sills extending in thefore and aft direction along either side edge of the floor panel; acenter frame extending in the fore and aft direction along alongitudinal center line of the floor panel; and a pair of connectingmembers each having a front end connected to a rear end of thecorresponding front side frame and a pair of bifurcated rear endsconnected to a front end of the corresponding side sill and a front endof the corresponding center frame, respectively; wherein a crotchportion of each connecting member is connected to a front end of thefloor frame, and each front side frame and the corresponding floor frameare connected in mutual alignment in the fore and aft direction in planview via the corresponding connecting member.
 2. The vehicle bodystructure according to claim 1, wherein a rear part of the floor panelis formed with a foot rest recess recessed from a remaining part of thefloor panel, a front end of the foot rest recess including a slopesection inclining upward toward a front part of the floor panel, andwherein the side bead extends across the foot rest recess in the foreand aft direction, and has a front end connected to a rear end of thecorresponding floor frame at the slope section in linear alignment witheach other.
 3. The vehicle body structure according to claim 2, whereinthe rear end of the floor frame is overlaid on an outer periphery of thefront end of the corresponding side bead by a certain longitudinallength.
 4. The vehicle body structure according to claim 2, furthercomprising a second middle cross member extending laterally immediatelyin front of the slope section.
 5. The vehicle body structure accordingto claim 1, wherein each side bead is formed as a groove having an openend facing upward, and a wire harness is received in the groove definedby the side bead.
 6. The vehicle body structure according to claim 1,wherein the floor panel is provided with a center tunnel section bulgingupward and extending in the fore and aft direction in a laterallycentral position of the floor panel, and the center frames extend alongeither side end of the center tunnel section.
 7. The vehicle bodystructure according to claim 6, wherein a part of the floor paneladjoining the center tunnel section includes a sloping section incliningupward toward the center tunnel section and a horizontal terracedsection connected to an inboard side of the sloping section, and anoutboard side of each center frame comprises a flange overlaid andwelded to the terraced section.
 8. The vehicle body structure accordingto claim 1, wherein the floor panel includes a downward bulge having abottom surface recessed from a general surface of the floor panel, andat least one bead projecting upward from a bottom wall of the downwardbulge and having a top surface substantially at a same elevation as thegeneral surface.
 9. The vehicle body structure according to claim 8,wherein the side bead extends in the fore and aft direction laterallyadjacent to the downward bulge.
 10. A vehicle body structure,comprising: a pair of front side frames each extending in a fore and aftdirection; a floor panel having a front end connected to rear ends ofthe front side frames and extending rearward from the front end thereofin a substantially horizontal direction; a first middle cross memberextending laterally in a rear end of the floor panel; a pair of floorframes attached to a lower surface of the floor panel, and each providedwith a front end connected to a rear end of the corresponding front sideframe and a rear end reaching at least to an intermediate part of thefloor panel in the fore and aft direction; and a pair of side beads eachhaving a front end connected to a rear end of the corresponding floorframe and extending rearward therefrom in the fore and aft direction tothe first middle cross member; wherein a rear part of the floor panel isformed with a foot rest recess recessed from a remaining part of thefloor panel, a front end of the foot rest recess including a slopesection inclining upward toward a front part of the floor panel, andwherein the side bead extends across the foot rest recess in the foreand aft direction, and has a front end connected to a rear end of thecorresponding floor frame at the slope section in linear alignment witheach other; the vehicle body structure further comprising a secondmiddle cross member extending laterally immediately in front of theslope section.
 11. A vehicle body structure, comprising: a pair of frontside frames each extending in a fore and aft direction; a floor panelhaving a front end connected to rear ends of the front side frames andextending rearward from the front end thereof in a substantiallyhorizontal direction; a first middle cross member extending laterally ina rear end of the floor panel; a pair of floor frames attached to alower surface of the floor panel, and each provided with a front endconnected to a rear end of the corresponding front side frame and a rearend reaching at least to an intermediate part of the floor panel in thefore and aft direction; and, a pair of side beads each having a frontend connected to a rear end of the corresponding floor frame andextending rearward therefrom in the fore and aft direction to the firstmiddle cross member; wherein each side bead is formed as a groove havingan open end facing upward, and a wire harness is received in the groovedefined by the side bead.
 12. A vehicle body structure, comprising: apair of front side frames each extending in a fore and aft direction; afloor panel having a front end connected to rear ends of the front sideframes and extending rearward from the front end thereof in asubstantially horizontal direction; a first middle cross memberextending laterally in a rear end of the floor panel; a pair of floorframes attached to a lower surface of the floor panel, and each providedwith a front end connected to a rear end of the corresponding front sideframe and a rear end reaching at least to an intermediate part of thefloor panel in the fore and aft direction; and a pair of side beads eachhaving a front end connected to a rear end of the corresponding floorframe and extending rearward therefrom in the fore and aft direction tothe first middle cross member; wherein the floor panel includes adownward bulge having a bottom surface recessed from a general surfaceof the floor panel, and at least one bead projecting upward from abottom wall of the downward bulge and having a top surface substantiallyat a same elevation as the general surface.
 13. The vehicle bodystructure according to claim 12, wherein the side bead extends in thefore and aft direction laterally adjacent to the downward bulge.
 14. Avehicle body structure, comprising: a pair of front side frames eachextending in a fore and aft direction; a floor panel having a front endconnected to rear ends of the front side frames and extending rearwardfrom the front end thereof in a substantially horizontal direction; afirst middle cross member extending laterally in a rear end of the floorpanel; a pair of floor frames attached to a lower surface of the floorpanel, and each provided with a front end connected to a rear end of thecorresponding front side frame and a rear end reaching at least to anintermediate part of the floor panel in the fore and aft direction; anda pair of side beads each having a front end connected to a rear end ofthe corresponding floor frame and extending rearward therefrom in thefore and aft direction to the first middle cross member; wherein thefloor panel includes a downward bulge having a bottom surface recessedfrom a general surface of the floor panel, and at least one beadprojecting upward from a bottom wall of the downward bulge, and whereinthe at least one bead is elongated in the fore and aft direction. 15.The vehicle body structure according to claim 14, wherein the downwardbulge is elongated in the fore and aft direction.
 16. The vehicle bodystructure according to claim 14, wherein the floor panel is providedwith a center tunnel section bulging upward and extending in the foreand aft direction in a laterally central position of the floor panel,and wherein the downward bulge is provided on each side of the centertunnel section.
 17. The vehicle body structure according to claim 16,wherein the pair of front side frames extend in the fore and aftdirection on either lateral side of a vehicle, and wherein each downwardbulge is positioned between the central tunnel section and thecorresponding side bead.
 18. The vehicle body structure according toclaim 14, wherein the at least one bead is configured to prevent saggingof a carpet placed on a part of the floor panel including the downwardbulge.